We study dark matter production
during the inflaton oscillation phase, which sets in immediately after inflation and
creates a non–adiabatic environment [1]}, [2]}, [3]}.
Using the effective field theory approach, we focus on the leading gravity–induced dim–6 operators assuming that the renormalizable couplings between the inflaton and dark matter
vanish. If DM is feebly interacting, its eventual abundance is determined by the number of DM quanta produced at this “preheating” stage. To this end, we
identify the dominant operator and study
whether it can be responsible for the correct
dark matter abundance.
